Abstract

Abstract Landscape composition has the potential to foster regulating ecosystem services such as pollination and biocontrol in temperate regions. However, most landscape studies do not take pesticide use into account even though it is the main control strategy worldwide and has negative impacts on beneficial insects. Moreover, few studies have explored these combined effects in smallholder cropping system with diverse landscapes and small cultivated parcels. We assessed the effect of semi-natural cover and pesticide use on pollinator and herbivore abundances and functions in 9 fields in the Ecuadorian Andes through participatory experiments with smallholder farmers. We performed a path analysis to quantify the effects of landscape and pesticide use on herbivory, pollination and ultimately yield. Pesticide use significantly reduced pollinator abundance but had no significant effect on pest abundance. Similarly, we found non-significant effects of landscape composition on either herbivory and pollination. The study also provides new information on understudied Andean lupine's pests and pollinators, whose application for small farmers is discussed. Finally, we hypothesize that peculiarities of tropical smallholder cropping systems and landscapes could explain the non-significant landscape effects on insect-based processes, which calls for more research in places outside the well-studied temperate region.

Highlights

  • Smallholder farmers in developing countries are heavily dependent on insecticides for herbivorous pest control (Schreinemachers and Tipraqsa 2012)

  • This study focuses on the Andean lupine (Lupinus mutabilis Sweet), a legume crop cultivated in the tropical Andes for its edible beans rich in proteins

  • 0.014; path-coefficient = 0.776; Fig. 3) arose between apex borer abundance and herbivory, reflecting the capacity of apex borer to modify plant architecture. This hypothesis was supported by the significantly lower herbivory for plants excluded from insects (p < 0.001; Fig. 4A) with a mean Apical Dominance Index (ADI) 25.7% higher compared to excluded plants (Welch Two Sample t-test: t(428.29) = 13.739, p < 0.0001)

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Summary

Introduction

Smallholder farmers in developing countries are heavily dependent on insecticides for herbivorous pest control (Schreinemachers and Tipraqsa 2012). Most of these insecticides have a broad spectrum of action (e.g. organophosphates, carbamates) and can harm non-target organisms (Gill and Garg 2014). Among the non-target insects, some are beneficial for crop production, such as natural enemies and pollinators. When natural enemies (predators and parasitoids) are killed by pesticides but a moderate number of pests survive, pest outbreaks may occur due to a decrease in biological pest control (Dutcher 2007). When pollinators are killed by pesticides, it reduces the pollination service for the crop and triggers a reduction in yield, if the crop is dependent on animal-mediated pollination. Pesticide use against a phytophagous insect can lead to undesired adverse consequences on both biocontrol and pollination

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